The huge story out of last week's UK parliamentary elections was that Prime Minister Theresa May's decision to call them backfired spectacularly. Less noticed here, but perhaps with much larger implications for American politics, was where Tories suffered their most embarrassing losses: the constituencies where a Labour victory, especially one led by the likes of Jeremy Corbyn, would have utterly unthinkable several years ago. By just 187 votes, Labour captured the tony London constituency of Canterbury for the first time since 1918. In an even more massive shock, Labour pulled off a 20-vote upset in even more posh Kensington & Chelsea, home to the likes of William & Kate, J.K. Rowling, Richard Branson and Elton John—a result even the most pessimistic Tories didn't see coming.

House Republicans ought to take notice. Just as Brexit and President Trump's election were once unthinkable, so too was the idea Democrats could retake the House before the 2022 round of redistricting. But amid Trump's unpopularity, Democrats' route to the majority runs directly through many of the districts Republicans have held the longest and

More from the Cook Political Report